The present invention relates to the field of radio-frequency identification tags and more particularly the manufacture thereof.
Radio-frequency identification tags also known as RFID tags are well-known for identifying all sorts of goods or objects, notably clothing or any laundry items.
For this purpose, the RFID tag must generally be flexible and be capable of withstanding a certain number of treatments applied throughout the period of use thereof, i.e. repeated washing, ironing and folding operations.
For this type of object, it is known, from the document WO 2012/126063 filed by the present applicant, to embody RFID tags with a particular textile material compatible with ultrasonic welding operations. The RFID tag usually includes a radio-frequency identification module (or RFID module), such as the MUTRAK™ module marketed by TAGSYS, and an external electrical antenna coupled with this module, these two components being attached to a strip of textile material.
The process for manufacturing this tag generally comprises the following steps:
1) weaving the electrical antenna in a strip of textile material; the electrical antenna conventionally consists of two wires of 90 twisted strands of stainless metal alloy and it is woven at the same time as the textile strip or after same; alternatively, the antenna may be sewn onto the textile strip after the weaving thereof;
2) depositing an adhesive layer onto the textile strip at the point where the RFID module is to be attached or on the inside of the RFID module to attach the RFID module at the envisaged location, the RFID module being positioned with respect to the electrical antenna so as to optimise the electromagnetic coupling thereof; the adhesive layer is generally an adhesive performing cold bonding of the RFID module on the textile strip;
3) folding the strip of textile material in half so as to place the RFID module and the electrical antenna between two half-strips of textile material; alternatively, a second textile strip may be affixed to the first strip to cover the RFID module and the antenna;
4) welding the two half-strips or the second strip by ultrasound so as to make same melt at least partially around the RFID module and optionally the electrical antenna so as to hold the RFID module mechanically in position between these two strips or half-strips.
The weaving step is generally preceded by a step for cladding the conductive wires of the antenna to reduce wear by abrasion from the weaving tool of the textile material backing.
This manufacturing method has drawbacks including:
this manufacturing process requires the use of costly fabrics which are compatible with the ultrasonic welding technique; this excludes for example the use of materials such as cotton which do not melt under ultrasonic or heat treatment;
it is necessary to clad the antenna wire to weave same with the textile material in order to reduce wear by abrasion from the weaving tool;
ultrasonic welding is relatively difficult to control in terms of positioning as it is necessary to avoid damaging the antenna and the RFID module; and
the manufacturing process comprises numerous steps; the tag is thus complex to embody.
The document WO2013/093826 also describes a method for manufacturing RFID tags wherein the electrical antenna is formed and then deposited on an adhesive layer previously deposited on a paper backing. The RFID module is then connected directly by welding at two points of the electrical antenna. This method has always had the drawback of requiring a welding step that is complex to implement.
The patent EP 2 405 054 also describes a method for embodying RFID tags wherein the textile backing comprises a pocket wherein the RFID module is inserted. This RFID module comprises an RFID chip and a near-field antenna connected to the chip. The tag also comprises a far-field antenna comprising a curved portion enclosing at least partially a circumference of the RFID chip. This far-field antenna is applied by sewing, by laser printing or by bonding to the pocket. The far-field antenna is not protected as it is applied or mounted on the textile backing comprising the pocket. The method further comprises a step for closing, for example by sewing, the pocket, which is complex to carry out on a tag including raised-surface portions (pocket equipped with the RFID module). The same applies for the step for applying the far-field antenna.